The skin is a complex organ with 3 major tissue layers: the epidermis, dermis and hypodermis. Skin structure, as well as its different cell types, organization and role have been described in numerous publications. In order to understand the impact of substances such as drugs, natural extracts, and ultraviolet radiation on the skin, non-animal tests have been developed and are now used successfully in the study of skin damage/repair (Auger 2004; Rouabhia 1997; Van de Sandt 1999).
Anti-oxidants significantly prevent tissue damage and stimulate wound healing. This is done through numerous mechanisms including prevention/limitation of lipid peroxidation, inflammation and alteration of cell DNA. Some plant extracts are believed to have strong anti-oxidant effects (Thang 2001).
Thylakoids are specialized membranes that are responsible for photosynthesis in eukaryotes (plant and algae) and prokaryotes (bacteria). These photosynthetic organisms convert CO2 to organic material by reducing this gas to carbohydrates in a complex set of reactions. Electrons for this reduction reaction ultimately come from water, which is then converted to oxygen and protons. Energy for this process is provided by light, which is absorbed by pigments (primarily chlorophylls and carotenoids).
The skin is an interface between the body and the environment and is continuously exposed to both endogenous and environmental factors that can cause damage and accelerate skin aging. Oxidative stress from free radicals or reactive oxygen species (ROS) is considered to be a major contributor to the process of aging. The ROS are produced by normal chemical reactions in the body as well as by UV radiation, pollution, smoking, stress and other external factors. It has been demonstrated that, during ageing, ROS levels rise in the skin while the antioxidant defenses decline. Oxidative stress is involved in the damage of cellular constituents, such as DNA, cell membrane lipids and proteins. Therefore, antioxidants applied topically can play a key role in reducing the damage caused by free radicals in the skin.
Lipid peroxidation is a well-established mechanism of cellular injury in both plants and animals, and is used as an indicator of oxidative stress in cells and tissues. Lipid peroxides, derived from polyunsaturated fatty acids, are unstable and decompose to form a complex series of compounds. These include reactive carbonyl compounds, of which the most abundant is malondialdehyde (MDA). Measurement of MDA, therefore, is widely used as an indicator of lipid peroxidation (Esterbaur, 1991). Increased levels of lipid peroxidation products have been associated with a variety of chronic diseases in both humans and model systems. The thiobarbituric acid reactive substances (TBARS) assay is commonly used to measure MDA in biological samples. However, this reaction is relatively nonspecific as both free and protein-bound MDA can react.
The MDA-586 method is designed to assay free MDA or, after a hydrolysis step, total MDA (i.e., free and protein-bound Schiff base conjugates). The assay conditions serve to minimize interference from other lipid peroxidation products, such as 4-hydroxyalkenals.
UVB irradiation (280-320 nm) is well absorbed in various biological macromolecules such as proteins, lipids, and DNA causing damage directly by converting the irradiation energy to photochemical reactions. In addition, ROS (e.g. oxygen radicals and singlet oxygen) are produced, which can modify the cellular DNA and other cellular components, possibly leading to photo-carcinogenesis. The UVA component of solar radiation (320-400 nm) has also been shown to produce deleterious biological effects in which singlet oxygen plays a major role. This is of particular importance in tissue that is exposed to UVA irradiation, such as the skin and the eye.
Skin is frequently exposed to sunlight, and UVA exposure is thought to cause skin aging and skin cancer mainly through the action of singlet oxygen. Singlet oxygen mediates gene regulation via the transcription factor activator protein-2, activates stress-activated protein kinases, or induces in skin fibroblasts a pattern of mitogen-activated protein kinase as well as an induction of p38 and c-Jun-N-terminal kinase.
A limited number of molecules in tissue weakly absorb UVA irradiation. After UVA irradiation absorption, these molecules (endogenous photo-sensitizer) crossover to its long-lived triplet state that allows transferring energy to oxygen molecules. The transferred energy leads to an energetically excited oxygen molecule (singlet oxygen), which is highly reactive.
It is well known that t-butyl hydroperoxide (tBHP) mimics the lipid peroxidation on skin (human keratinocytes). tBHP is an organic peroxide used to induce free radical production in several biological systems. Red cells exposed to tBHP undergo lipid peroxidation, haemoglobin degradation and hexose monophosphate-shunt stimulation. Lipid peroxidation and haemoglobin degradation represent extremes of a spectrum of oxidative damage. tBHP induces cell death via apoptosis or necrosis. Erythrocyte haemolysis assay is one of the best cellular models to evaluate the anti-oxidative effect of a compound.
A dynamic and intact thylakoid membrane extract having both anti-oxidative and anti-inflammatory properties, and its use in combination with other anti-inflammatory compounds, have been described in International patent publication numbers WO 01/49305 and WO 01/04042, respectively. The anti-oxidative and anti-inflammatory properties of the thylakoid extract have been demonstrated in in vitro, ex vivo, in situ and in vivo studies. Specifically, the thylakoid extract has been shown to capture the noxious reactive oxygen species including singlet oxygen species, and to modulate pro- and anti-inflammatory cytokines toward attenuation of inflammation.
The use of thylakoid extracts as ROS scavengers, as photoprotectors, particularly against ultraviolet (UV) radiations, and as a solar screen because of its capacity to capture UV radiations and to dissipate the solar energy into heat, has also been described (WO 01/49305).
Furthermore, US 20070036877 discloses that, in vivo, topical applications of the thylakoid extract applied directly to the site of injury, have been shown to prevent or reduce the UV-induced skin damage in hairless mice.
There is a need for cosmetic and topical compositions containing an effective amount of a photosynthetic cell extract comprising a functional thylakoid system (“photosynthetic cell extract” or “extract”) and having anti-wrinkle and anti-aging effects on a user's skin. There is also a need for cosmetic and topical compositions containing an effective amount of the photosynthetic cell extract to provide prolonged protection of the skin against ultraviolet A (UVA) and ultraviolet (UVB) damage.